Clinical trials to reduce heavy alcohol use in people living with HIV (PLWH) and those at high risk for HIV infection are currently being conducted through NIAAA-supported Consortia for HIV/AIDS and Alcohol-Related Outcomes Research Trials (CHAARTs). The overall objective of this proposal is to maximize the information gleaned from these trials to enable better design of evidence-based alcohol-HIV counseling interventions. While a good deal is known from the Motivational Interviewing literature about mechanisms of behavior change in counseling approaches for alcohol and other substance use, little is known about change mechanisms in interventions that focus on sexual risk behaviors or medication adherence, and there is a dearth of work on mechanisms of multiple behavior change. To address this gap, we will create a Mechanisms of Behavior Change Resource Core (MBCRC) within the Brown University Alcohol Research Center on HIV that will code provider-patient dialogues in five ongoing CHAART trials using two distinct coding systems. Specifically, we will adapt the Motivational Interviewing Skills Code to code both alcohol and HIV-relevant provider and patient language in alcohol-HIV interventions and apply the Generalized Medical Interaction Analysis System to examine factors that influence outcomes in alcohol-HIV interventions outside of motivationally-focused behavior change counseling. Overall, the MBCRC will transcribe and code provider-patient interactions across approximately 1,000 20-90, minute intervention sessions from four ongoing randomized clinical trials and one implementation study. Coding data will be used to predict future alcohol use, acceptance and use of alcohol pharmacotherapy, high-risk sex, HAART adherence, and HIV testing. Results will provide crucial insights about provider behaviors and skills that are most effective in fostering changes in drinking and HIV-relevant behaviors in identified high-risk populations, as well as key barriers to change. Results will have direct relevance (a) for training providers who work with HIV patients and those at high risk for HIV infection and (b) for the improvement and implementation of alcohol-HIV interventions in a range of contexts and populations.